Refactor FuseReadReturnedDataTest to make VirtualTestFile reusable for the upcoming write tests

src/test/testutils/VirtualTestFile.cpp

@@ -0,0 +1,44 @@
+#include "VirtualTestFile.h"
+
+#include <algorithm>
+#include <cstring>
+
+using std::min;
+
+VirtualTestFile::VirtualTestFile(size_t size): _fileData(new char[size]), _size(size) {
+  fillFileWithRandomData();
+}
+
+VirtualTestFile::~VirtualTestFile() {
+  delete[] _fileData;
+}
+
+void VirtualTestFile::fillFileWithRandomData() {
+  long long int val = 1;
+  for(size_t i=0; i<_size/sizeof(long long int); ++i) {
+    //MMIX linear congruential generator
+    val *= 6364136223846793005L;
+    val += 1442695040888963407;
+    reinterpret_cast<long long int*>(_fileData)[i] = val;
+  }
+}
+
+int VirtualTestFile::read(void *buf, size_t count, off_t offset) {
+  size_t realCount = min(count, _size - offset);
+  memcpy(buf, _fileData+offset, realCount);
+  return realCount;
+}
+
+bool VirtualTestFile::fileContentEqual(char *content, size_t count, off_t offset) {
+  return 0 == memcmp(content, _fileData + offset, count);
+}
+
+VirtualTestFileWriteable::VirtualTestFileWriteable(size_t size)
+  :VirtualTestFile(size) {
+  originalFileData = new char[size];
+  memcpy(originalFileData, _fileData, size);
+}
+
+VirtualTestFileWriteable::~VirtualTestFileWriteable() {
+  delete[] originalFileData;
+}

src/test/testutils/VirtualTestFile.h

@@ -0,0 +1,33 @@
+#pragma once
+#ifndef TEST_TESTUTILS_VIRTUALTESTFILE_H_
+#define TEST_TESTUTILS_VIRTUALTESTFILE_H_
+
+#include <cstdio>
+
+class VirtualTestFile {
+public:
+  VirtualTestFile(size_t size);
+  virtual ~VirtualTestFile();
+
+  int read(void *buf, size_t count, off_t offset);
+
+  // Return true, iff the given data is equal to the data of the file at the given offset.
+  bool fileContentEqual(char *content, size_t count, off_t offset);
+
+protected:
+  char *_fileData;
+  size_t _size;
+
+private:
+  void fillFileWithRandomData();
+};
+
+class VirtualTestFileWriteable: public VirtualTestFile {
+public:
+  VirtualTestFileWriteable(size_t size);
+  virtual ~VirtualTestFileWriteable();
+private:
+  char *originalFileData;
+};
+
+#endif